Abstract

Objective Juvenile idiopathic arthritis (JIA) consists of a heterogeneous group of infl ammatory disorders, within which there are a number of clinical subgroups. Diagnosis and assignment to a particular subgroup can be problematical and more concise methods of subgroup classifi cation are required. This study of the synovial membrane characterises the immunohistochemical features in early untreated, newly diagnosed JIA and compares fi ndings with disease subgroup at 2 years.Methods 42 patients with newly diagnosed untreated JIA underwent synovial biopsy before the administration of steroids or disease-modifying antirheumatic drugs. Patients were classifi ed as either polyarticular, persistent oligoarticular or extended-to-be oligoarticular. The location and semiquantitative analysis of T-cell subsets, B cells, macrophages and blood vessels were determined using immunohistochemistry.Results Synovial hyperplasia varied signifi cantly between the three groups (p<0.0001). There was a signifi cant difference in the CD3 T-cell population between the three groups (p=0.004) and between the extended-to-be and persistent group (p=0.032). CD4 expression was signifi cantly higher in the poly and extended-to-be oligo groups (p=0.002), again the extended-to-be group had more CD4 T cells than the persistent group (p=0.008). B-cell infi ltrates were more marked in the polyarticular group and were signifi cantly higher in the extended-to-be group compared with the persistent group (p=0.005). Vascularisation was more pronounced in the polyarticular and extended-to-be oligoarticular groups, the extended-to-be group had signifi cantly more vascularisation than the persistent group (p=0.0002).Conclusions There are signifi cant differences in the histomorphometric features of synovial tissue between patient subgroups. Immunohistological examination of synovial membrane biopsies may provide further insight into early disease processes in JIA.